The cells of the TCZ (turquoise) are organized into CD8+ T cells (maroon) in the center and CD4+ T cells (orange) in the outer TCZ. This organization enables rapid formation of necessary cellular contacts, after migration within the WP, for the response to an immunologic insult. Shown are selected, dominant immune reactions in the spleen relevant to each insult. (A) Listeria induces rapid migration of cDC1s (silver) into the central TCZ where they present antigen and prime CD8+ T cells. (B) Transfusion of xenogeneic or allogeneic RBCs induces migration of cDC2s (black) to the outer TCZ, for CD4+ T cell priming and effective B cell antibody production (with the LZ, light zone, and DZ, dark zone, of a germinal center, GC, shown). (C) Malaria-infected RBCs induce a poorly coordinated and slow humoral immune response that includes disintegration of WP-RP border, MZ disruption and GC disorganization. After repeated infections, protective antibodies are ultimately produced.